The present invention relates to a focus control apparatus, and method. The present invention is suitable for, for example, an image pickup apparatus such as a video camera, an electronic still camera and a camera mechanism part of a portable telephone, equipped with an auto focus function.
A large number of conventional image pickup apparatuses such as surveillance cameras and DVD (Digital Versatile Disc) cameras are equipped with the auto focus function to automatically adjust the focus. As a focusing scheme in such an auto focus function, there is a contrast scheme in which focus adjustment is conducted by utilizing the fact that an in-focus state is attained in a position where the amplitude of the contrast signal of a picked up video image is maximized.
In the image pickup apparatus, the picked up video image is brought out of focus or in focus by moving a focus lens in its optical axis direction. As a result, the amplitude of the contrast signal also changes. In the most basic contrast scheme, the focus lens is temporarily moved in its optical axis direction, a direction in which the in-focus state is attained is detected on the basis of whether the amplitude of the contrast signal increases after the movement as compared with before the movement, and the focus lens is moved in that direction.
In JP3079622(B2), JP3338322(B2) and JP4034409(B2), techniques concerning focus control using the contrast scheme are disclosed. A method disclosed in JP-A-7-318795 and JP-A-9-133854 as a focusing processing method using the contrast scheme includes providing a narrow band high frequency band component detector to detect high frequency band components from a video signal and a wide band high frequency band component detector to detect high frequency band components inclusive of frequency components lower in frequency than the high frequency band components, dividing wide band data obtained as a result of the detection from the wide band high frequency band component detector by narrow band data obtained as a result of the detection from the narrow band high frequency band component detector with a microcomputer, regarding a result of the division as a focus evaluation value, and exercising focus control of the image pickup apparatus on the basis of the focus evaluation value.